<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .top {
            width: 100%;
            height: 80px;
            margin: auto;
            background-color: #ccc;
            border: 2px dashed rgb(107, 107, 107);
            text-align: center;
            line-height: 80px;
        }

        .banner {
            width: 100%;
            height: 60px;
            margin: 5px auto;
            background-color: #ccc;
            border: 2px dashed rgb(107, 107, 107);
            text-align: center;
            line-height: 60px;

        }

        .main {
            width: 100%;
            /*height: 500px;*/
            margin: auto;
            /* background-color: #ccc; */
            /* border: 2px dashed rgb(107, 107, 107); */
            /*text-align: center;*/
            /*line-height: 500px;*/
            /*overflow: hidden;*/
        }

        .main-left {
            height: 500px;
            width: 200px;
            background-color: #ccc;
            border: 2px dashed rgb(107, 107, 107);
            float: left;
            /*margin-right: 880px;*/
        }

        .main-right {
            float: right;
            height: 500px;
            width: 200px;
            background-color: #ccc;
            border: 2px dashed rgb(107, 107, 107);
            /*margin-left: 210px;*/
        }

        .main-content {
            height: 500px;
            width: 520px;
            background-color: #ccc;
            border: 2px dashed rgb(107, 107, 107);
            margin-left: 210px;
        }

        .footer {
            width: 100%;
            height: 120px;
            margin: auto;
            background-color: #ccc;
            border: 2px dashed rgb(107, 107, 107);
            text-align: center;
            line-height: 120px;
            margin-top: 5px;
        }

        .clearfix:after {
            content: '';
            display: block;
            clear: both;
        }
    </style>
</head>

<body>
    <div class="top">top</div>
    <div class="banner">banner</div>
    <div class="main clearfix">
        <div class="main-left">left</div>
        <div class="main-right">right</div>
        <div class="main-content">content</div>
        <!--<div class="main-right">right</div>-->
    </div>
    <!--<div style="clear: both;"></div>-->
    <div class="footer">footer</div>
</body>

</html>